Reactor for removing impurities from a liquid

Abstract: The present invention concerns a reactor for removing impurities from a liquid, in particular for de-inking, including a tank (1) within which the liquid to be purified together with a gas or air is introduced (2-3); a drain of the purified accepted through an outlet (7) of said tank (1); inlets (8-11, 9-12, 10-13) at different heights of the tank (1) connected to said purified liquid outlet (7) together with the inlet of gas or air; a rotating shaft (18) inside the tank (1) carrying blades (20, 21, 22, 23) at the different heights of the tank within which the liquid together with gas or air is introduced.; the blades (20, 21, 22, 23) have progressively increasing heights when moving towards the lower portion of the tank (1). The invention also concerns the method embodied by the above-described reactor.

Description: The present invention concerns a reactor for removing impurities from a liquid, in particular for de-inking suspensions deriving from printed waste paper. Apparatuses are known for removing impurities from liquids and in particular for de-inking paper suspensions, said apparatuses being based on the flotation method. For example US 4 094 783 relates a separator for removing impurities from a contaminated liquid including: a tank having an upper and a lower portion; a main inlet in said upper portion, and gas or air inlet means connected to said main inlet, the liquid to be purified being introduced together with gas or air in said tank through said main inlet; an outlet located in the lower portion of said tank to drain off the purified liquid; and inlets at different heights in the tank connected to said purified liquid outlet, and gas or inlet means connected to said inlets, a portion of the purified liquid being continuously introduced together with air or gas in the tank at said different heights through said inlets, with the drawback that this patent does not solve the problem to provide a reactor and method for improving the purification efficiency while increasing pulp density and cleaning of the light polluting portions. On the contrary the present invention as defined in claims 1 to 8 solves the problem eliminating such drawback with the introduction of a portion of the purified liquid with air or gas at different heights in the tank in the positions where different blades are rotating for stirring the liquid, with further features that the stirring is increased from the upper portion towards the lower portion of the tank and that the liquid together with the gas or air is pushed towards the central area of the tank while being stirred. Other patents as EP 0 037 513, DE 3 524 071 and US 5 096 572 relate to reactors for removing impurities from a liquid, but also all such prior patents do not solve the problem of the present invention. Further characteristics and advantages of the invention will be apparent from the following detailed description of a preferred but not exclusive embodiment thereof, illustrated merely as a non-limiting example in the annexed figures wherein: Fig.1 is a schematic sectional view of the present reactor; Fig.2 is a schematic horizontal cross section of fig.1; and Fig.3 is an outer side view of the reactor of fig.1. Referring to the figures, the present reactor includes a tank 1 within which, in the upper portion thereof, there is located the main inlet 2 of the liquid to be purified which is introduced mixed with a gas or air sucked in through duct 3 inserted into the inlet duct 2. The foam formed by bubbles enclosing the impurities, e.g. ink contained in the liquid introduced in the reactor, is removed by the rotating skimming blade 4 which directs said foam through the outlet duct 5. The skimming blade 4 is cleaned by water jets 6 located above the blade. In the meanwhile, the purified liquid flows down through the outlet 7 located at the center of the lower portion of tank 1. According to the main feature of the present invention, said tank 1 has inlets 8, 9, 10 at different heights, as it can be seen in fig.3, within which simultaneously flows the purified liquid discharged through outlet 7. Gas or air is sucked in through ducts 11, 12 and 13, respectively inserted into the liquid inlet ducts 8, 9 and 10. A portion of the purified liquid flowing out through outlet 7 is directed upwards according to arrow 7A towards container 14, provided with an internal wall 15, along which the purified liquid flows out through drain 16 according to arrow 17. Said tank 1 includes therein a rotating shaft 18 connected to motor 19 for its rotation. Said shaft 18 is provided with blades 20, 21, 22, 23 positioned at the different tank heights forming the washing beds, within which the liquid together with air or gas is introduced, as described above. Said blades increase in height when moving downwards, and have the function of breaking up the gas-liquid-fiber phase, in the case of paper mixtures, while their different height is due to the fact that the speed of the downflowing liquid increases when moving downwards, i.e. towards the bottom of tank 1. A further characteristic is that said blades are spiral-curved with the concavity facing the direction of the rotating motion of said shaft 18, i.e. according to arrow 24. Moreover, the blade rotation speed can be changed by means of a speed variator, in order to achieve a control of the chemical-physical reactions inside the reactor. As it is schematically shown in fig.1, The main inlet 2 of the liquid mixed with the gas or air is controlled by valve 25, while the inlets 8-11, 9-12, 10-13 of the purified liquid mixed with gas or air are controlled by valve 26. In brief, the operation of the above-described reactor and consequently the method for removing impurities from a liquid embodied by said reactor includes the steps of introducing the liquid mixed with air or gas in the upper portion of tank 1 and further introducing the purified liquid with air or gas simultaneously and continuously at different heights of tank 1 in the various washing beds, said purified liquid coming according to arrow 72 from outlet 7 of tank 1 and letting out a portion of said purified liquid as accepted liquid through drain 16. Furthermore, the stirring of the liquid by means of blades 20, 21, 22, 23 increases when moving down from the upper portion to the lower portion of tank 1, according to the different blade height, as described above, and the liquid is simultaneously pushed towards the central area of tank 1 by the particular spiral shape of blades 20, 21, 22, 23 in order to carry out the washing of the liquid with air on each horizontal section of the tank.

Claims: A reactor for removing impurities from a liquid, in particular for de-inking, said reactor including: a tank (1) having an upper and a lower portion; a main inlet (2) in said upper portion, and gas or air inlet means (3) connected to said main inlet (2), the liquid to be purified being introduced together with gas or air in said tank (1) through said main inlet (2); an outlet (7) located in the lower portion of said tank (1) to drain off the purified liquid; inlets (8, 9, 10) at different heights in the tank (1) connected to said purified liquid outlet (7), and gas or inlet means (11, 12, 13) connected to said inlets (8, 9, 10), a portion of the purified liquid being continuously introduced together with air or gas in the tank (1) at said different heights through said inlets (8, 9, 10); characterized in that it comprises a rotary shaft (18) in the tank (1), said rotary shaft (1) being provided with blades (20, 21, 22, 23) suitable to stir the liquid at the different heights of the tank (1) within which the liquid is introduced together with gas or air. A reactor according to claim 1, characterized in that said blades (20, 21, 22, 23) have progressively increasing heights when moving from the upper portion towards the lower portion of the tank (1). A reactor according to any of the preceding claims, characterized in that said blades (20, 21, 22, 23) are spiral-curved with the concavity facing the direction of rotation of said shaft (18). A reactor according to any of the preceding claims, characterized in that it is provided with a means (19) for rotating said rotary shaft (18) through which the rotation speed of the blades (20, 21, 22, 23) can be changed. A method for removing impurities from a liquid comprising the following steps: introducing the liquid to be purified together with air or gas in the upper portion of a tank (1), and removing the purified liquid from the lower portion of the tank (1); and simultaneously and continuously introducing in the tank (1) a portion of the purified liquid removed from the lower portion of the tank (1), the purified liquid being introduced at different heights of the tank (1) together with air or gas; the method being further characterized by the following steps: providing within the tank (1) a rotary shaft (18) with a plurality of blades (20, 21, 22, 23) for stirring the liquid together with air or gas at the different heights of the tank (1) within which the liquid is introduced together with air or gas; and stirring the liquid together with air or gas inside the tank (1) by rotating said blades (20, 21, 22, 23). A method according to claim 5, characterized in that the liquid together with gas or air is pushed towards the central areas of the tank (1) while being stirred. A method according to claims 5 or 6, characterized in that said stirring is increased from the upper portion to the lower portion of the tank (1). A method according to any of claims 5 to 7, characterized by rotating said blades (20, 21, 22, 23) at variable speed.

Inventors: MAGARAGGIA FLAVIO, MAGARAGGIA, FLAVIO
Applicants: COMER SPA, COMER S.P.A.
Application year: 1994
Main classification: D21B1
IPC codes: D21B1, D21F1